The present invention relates to an unfurling coiling device for a strip-shaped metal or plastic band as well as for a band made of a combination of such materials which, upon being unwound from a drum, forms itself into a self-supporting tubular structure, preferably for so-called overlapping tubes.
Overlapping tubes are known in the spacecraft industry by the acronym "STEM" (Storable Tubular Extendible Member). They serve to support extendible satellite parts. They are used, for example, as antennas, outriggers, instrument booms and as supports for solar cell panels or surfaces. In the paper by F. Rimrott, entitled "Entwurf und Berechnung von Lapprohren," (Design and Calculation for Overlapping Tubes) published in the periodical LUFTFAHRTTECHNIK RAUMFAHRTTECHNIK (Aeronautic Art, Space Travel Art) Volume 14, No. 1, January 1968, pages 1-6, and in a publication by the firm SPAR Aerospace Products Ltd., Toronto, Canada, entitled "The BI-STEM -- A New Technique in Unfurlable Structures," Preprint No. 18, May 4, 1967, these devices are described in general terms.
According to these publications, tubes which are to be overlapped when the tubular member is extended are presently being made of titanium, beryllium-copper, stainless steel and aluminum. They are produced in a continuous process from a thin strip having a selected width, any desired length, and a thickness which depends on the desired strength of the tube and which is generally several thousandths of an inch. The strip is shaped in stages into a cylindrical shape with overlap and then drawn through a circular orifice where it is stress-relieved at a temperature suitable for the particular material involved and then cooled. The thus resulting overlapped tube can now be flattened out again and wound on a drum. The potential energy stored in the longitudinally flattened, coiled tube is considerable and can be utilized to extend the tube.
A BI-STEM member is an extendible tube composed of two diametrically opposed strip elements each shaped from a thin strip to assume, when free to do so, a tubular shape having an essentially circular cross section. Thus, a BI-STEM, is a dual tube. However, in the case of BI-STEM structures, the cross section of each tubular element does not form a complete closed circle, but rather has an open, C-shaped cross section and thus defines a longitudinal slot. Since the lateral sides of such a tube do not overlap, and are, in fact, spaced apart in the extended tube, a tube having this form is sometimes referred to as "underlapped".
If the so-called BI-STEM is made of two tubes, which do not individually overlap, i.e. which are underlapped, but which overlap one another, and which are boxed one inside the other with their longitudinal center lines offset by 180.degree. and are wound either on a common drum or each on a separate drum, a distinction is made between a "single" or "twin" cassette, when speaking of the unfurling device.
An unfurling device for an overlapped tube which is driven by an electric motor is disclosed, for example, in U.S. Pat. No. 3,144,215.